Zoom lens and imaging apparatus

ABSTRACT

A zoom lens is provided, which includes a first lens group Gr 1  having positive refractive power, a second lens group Gr 2  having negative refractive power, which is movable in an optical axis direction mainly for zooming (varying power), a third lens group Gr 3  having positive refractive power, a fourth lens group Gr 4  having negative refractive power, which is movable in the optical axis direction for correcting fluctuations in focal position during zooming and for focusing, and a fifth lens group Gr 5  having positive refractive power, which lens groups are arrayed in order from an object side, wherein the first lens group includes a concave lens, a convex lens, and a triple-cemented lens T 1  in which a lens L 6  made of special low-dispersion glass is sandwiched in the middle, which lenses are arrayed in order from the object side. Thereby, a range from a super wide-angle area to a super telephoto area can be covered with angles of view of not less than 67 degrees at a wide-angle end and not more than 1.6 degrees at a telephoto end, various aberrations can be favorably corrected while providing a zoom ratio of about 40 times, and a zoom lens excellent in mass productivity can be attained.

TECHNICAL FIELD

The present invention relates to a novel zoom lens and a novel imagingapparatus. In particular, the present invention relates to an optimumzoom lens for a wide-angle, high-powered video camera covering from asuper wind-angle area to a super telephoto area, and to an imagingapparatus using the zoom lens.

BACKGROUND ART

In the design of a zoom lens for video camera for people's livelihood,as trends of taking advantage of a downsized imaging element, there area trend of aiming for downsizing with the same zoom ratio (variablepower rate) and a trend of aiming for higher power in zoom ratio with apractical size.

As an example of techniques for realizing the higher-powered zoom lensin the latter trend, there is one described in Japanese PatentApplication Publication No. 8-5913. This zoom lens is composed of fivelens groups in an arrangement of positive, negative, positive, negativeand positive refractive power in order from the object side, and atleast a second lens group and a fourth lens group are moved for zooming(varying power) and focusing to thereby obtain a zoom ratio of abouttwenty times.

However, if by making use of further downsizing of the imaging element,the power rate is increasingly made high, for example, if in order toobtain a zoom ratio of 40 times, the technique of Japanese PatentApplication Publication No. 8-5913 is applied as it is, the followingproblems have arisen. Namely, fluctuations in aberration by zooming,chromatic aberration and spherical aberration at a telephoto end, andthe like cannot be corrected. Therefore, in the technique of JapanesePatent Application Publication No. 8-5913, while the practical size of azoom lens is maintained, the realized power rate is limited to about 20times.

Consequently, in a technique described in Japanese Patent ApplicationPublication No. 2000-105336, in order to correct the fluctuations inaberration by zooming, the chromatic aberration and spherical aberrationat the telephoto end, and the like, which have been problems inrealizing the high power rate, aspherical lenses are introduced to athird lens group and a fifth lens group and a number of materials eachhaving a large Abbe number and abnormal partial dispersibility are usedto thereby realize an angle of view of not less than 85 degrees and azoom ratio of 40 times at a wide-angle end.

However, in the technique shown in the above-described Japanese PatentApplication Publication No. 2000-105336, three sheets of speciallow-dispersion glass each having a large Abbe number and abnormalpartial dispersibility are used. Since this special low-dispersion glasshas a soft quality and low latent flaw resistance as is well known,latent flaws are easily caused during ultrasonic cleaning in lensmanufacturing. Furthermore, since a thermal expansion coefficient of thespecial low-dispersion glass is large, when it is heated inside a vacuumchamber in a vapor deposition process for lens coating, and immediatelyafter the vapor deposition, air is caused to flow into the vacuumchamber to quench, cracks easily occur. Therefore, the glass needs to beleft inside the vacuum chamber for long hours after the vapor depositionto cool slowly, so that a vapor deposition cycle takes long, whichcauses a problem with productivity and further disadvantageously affectscosts.

Accordingly, the zoom lens shown in Japanese Patent ApplicationPublication No. 2000-105336 wherein three lenses made of speciallow-dispersion glass are used cannot be mass-produced, and thusunsuitable for zoom lens for people's livelihood.

Consequently, in light of the above-described problems, it is an objectof the present invention to provide a zoom lens which can cover from asuper wide-angle area to a super telephoto area with angles of view ofnot less than 67 degrees at a wide-angle end and not more than 1.6degrees at a telephoto end, whose various aberrations can be favorablycorrected while having a zoom ratio of about 40 times, and which isexcellent in mass productivity, and an imaging apparatus using the zoomlens.

DISCLOSURE OF THE INVENTION

In order to solve the above-described problems, a zoom lens of thepresent invention is an inner focus type having four or five lensgroups, including at least a first lens group having positive refractivepower, a second lens group having negative refractive power, which ismovable in an optical axis direction mainly for zooming (varying power),a third lens group having positive refractive power, and a fourth lensgroup having positive or negative refractive power, which is movable inthe optical axis direction for correcting fluctuations in focal positionduring zooming and for focusing, which lens groups are arrayed in orderfrom the object side, wherein the first lens group has at least aconcave lens, a convex lens, and a triple-cemented lens in which a lensmade of special low-dispersion glass is sandwiched in the middle, whichlenses are arrayed in order from the object side.

Furthermore, in order to solve the above-described problems, an imagingapparatus of the present invention includes a zoom lens, imaging meansfor transforming an image taken in by the zoom lens to an electricalimage signal, and image control means, wherein the image control means,referring to a transformation coordinate coefficient prepared in advanceaccording to a variable power rate by the zoom lens, moves points on theimage which are defined by the image signal formed by the imaging meansto form a new image signal subjected to coordinate transformation and tooutput the new image signal, and the zoom lens of an inner focus typehaving four or five lens groups, includes at least a first lens grouphaving positive refractive power, a second lens group having negativerefractive power, which is movable in an optical axis direction mainlyfor zooming (varying power), a third lens group having positiverefractive power, and a fourth lens group having positive or negativerefractive power, which is movable in the optical axis direction forcorrecting fluctuations in focal position during zooming and forfocusing, which lens groups are arrayed in order from the object side,the first lens group having at least a concave lens, a convex lens, anda triple-cemented lens in which a lens made of special low-dispersionglass is sandwiched in the middle, which lenses are arrayed in orderfrom the object side.

Accordingly, in the zoom lens and the imaging apparatus of the presentinvention, a range from a super wide-angle area to a super telephotoarea can be covered with angles of view of not less than 67 degrees at awide-angle end and not more than 1.6 degrees at a telephoto end, variousaberrations can be favorably corrected while providing a zoom ratio ofabout 40 times, and the lens made of special low-dispersion glass islocated in the middle of the triple-cemented lens, so that latent flawsare not caused during ultrasonic cleaning even if lens coating is notapplied.

Furthermore, latent flaws caused at the time of lens polishing or duringultrasonic cleaning can be filled with an adhesive material between thecemented lens and the cementing makes coating unnecessary.

The invention described in claims 1, 9 and 21 is characterized in thatthe zoom lens is an inner focus type having four or five lens group,including at least a first lens group having positive refractive power,a second lens group having negative refractive power, which is movablein an optical axis direction mainly for zooming (varying power), a thirdlens group having positive refractive power, and a fourth lens grouphaving positive or negative refractive power, which is movable in theoptical axis direction for correcting fluctuations in focal positionduring zooming and for focusing, which lens groups are arrayed in orderfrom the object side, wherein the first lens group has at least aconcave lens, a convex lens, and a triple-cemented lens in which a lensmade of special low-dispersion glass is sandwiched in the middle, whichlenses are arrayed in order from the object side.

Accordingly, in the invention described in claims 1, 9 and 21, there canbe obtained the zoom lens which can cover from the super wide-angle areato the super telephoto area with the angles of view of not less than 67degrees at the wide-angle end and not more than 1.6 degrees at thetelephoto end, and whose various aberrations can be favorably correctedwhile having a zoom ratio of about 40 times. Furthermore, since the lensmade of special low-dispersion glass is located in the middle of thetriple-cemented lens, latent flaws are not caused during ultrasoniccleaning even if lens coating is not applied, dents and latent flawscaused at the time of lens polishing and during ultrasonic cleaning canbe filled with an adhesive agent located between the cemented lens, andthe cementing makes the coating unnecessary, so that a zoom lensexcellent in mass productivity can be attained at a low cost.

In the invention described in claims 2, 10 and 22, the triple-cementedlens in the first lens group includes a first concave lens A1, a convexlens A2 formed of special low-dispersion glass and a second concave lensA3, which lenses are arrayed in order from the object side, and thefirst concave lens A1 and the convex lens A2 are formed of materialssatisfying two conditional formulae (1) n1−n2>0.3, and (2) |v1−v2|>40,wherein refractive indexes at a line C, a line d, a line F and a line gare nC, nd, nF and ng, respectively, and nx is a refractive index nd atthe line d of a lens Ax (an xth lens from the object side among thetriple-cemented lens, hereinafter, this is the same), and vx is an Abbenumber vd=(nd−1)/(nF−nC) at the line d of the lens Ax. Consequently,primary chromatic aberration, particularly primary chromatic aberrationat the telephoto end can be favorably corrected, which contributes tothe realization of the high power rate of 40 times.

In the invention described in claims 3, 4, 11, 12, 23 and 24, thetriple-cemented lens in the first lens group includes a first concavelens A1, a convex lens A2 formed of special low-dispersion glass and asecond concave lens A3, which lenses are arrayed in order from theobject side, and the convex lens A2 and the second concave lens A3 areformed of materials satisfying three conditional formulae (3)|n2−n3|<0.1, (4) v23>80, and (5) ΔP23>0.03, wherein refractive indexesat a line C, a line d, a line F and a line g are nC, nd, nF and ng,respectively, and nx is a refractive index nd at the line d of a lens Ax(an xth lens from the object side among the triple-cemented lens,hereinafter, this is the same), and vx is an Abbe numbervd=(nd−1)/(nF−nC) at the line d of the lens Ax, and Px is a partialdispersion ratio P=(ng−nF)/(nF−nC) of the lens Ax. Consequently,secondary chromatic aberration on the telephoto side, and sphericalaberration, coma aberration, and axial chromatic aberration at thetelephoto end can be favorably corrected.

In the invention described in claims 5 to 8, and claims 25 to 28, thefirst lens group includes a first lens of a concave meniscus lens whoseconvex surface faces the object side, a second lens of a convex lens, atriple-cemented lens made of a third lens of a concave meniscus lenswhose convex surface faces the object side, a fourth lens of a convexlens and a fifth lens of a concave meniscus lens whose concave surfacefaces the object side, and a sixth lens of a convex lens, which lensesare arrayed in order from the object side. Consequently, the correctionof curved field, distortion aberration and spherical aberration isfacilitated.

In the invention described in claims 13 to 16, the first lens groupincludes a first lens of a concave meniscus lens whose convex surfacefaces the object side, a second lens of a convex lens, a third lens of aconcave meniscus lens whose convex surface faces the object side, afourth lens L4 of a convex lens, a triple-cemented lens made of a fifthlens of a concave meniscus lens whose convex surface faces the objectside, a sixth lens of a convex lens and a seventh lens of a concavemeniscus lens whose concave surface faces the object side, and an eighthlens of a convex lens, which lenses are arrayed in order from the objectside. Consequently, the correction of curved field, distortionaberration and spherical aberration is facilitated.

In the invention described in claims 17 to 20, the first lens groupincludes a first lens of a concave meniscus lens whose convex surfacefaces the object side, a second lens of a convex lens, a cemented lensmade of a third lens L3 of a concave meniscus lens whose convex surfacefaces the object side and a fourth lens of a convex lens, atriple-cemented lens made of a fifth lens of a concave meniscus lenswhose convex surface faces the object side, a sixth lens of a convexlens and a seventh lens of a concave meniscus lens whose concave surfacefaces the object side, and an eighth lens of a convex lens, which lensesare arrayed in order from the object side. Consequently, the correctionof curved field, distortion aberration and the spherical aberration isfacilitated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first embodiment of a zoom lens of the present inventiontogether with FIGS. 2 to 4, and is a schematic view showing a lensconfiguration.

FIG. 2 is charts showing spherical aberration, astigmatism anddistortion aberration at a wide-angle end.

FIG. 3 is charts showing spherical aberration, astigmatism anddistortion aberration at an intermediate focal position between thewide-angle end and a telephoto end.

FIG. 4 is charts showing spherical aberration, astigmatism anddistortion aberration at the telephoto end.

FIG. 5 shows a second embodiment of a zoom lens of the present inventiontogether with FIGS. 6 to 8, and is a schematic view showing a lensconfiguration.

FIG. 6 is charts showing spherical aberration, astigmatism anddistortion aberration at a wide-angle end.

FIG. 7 is charts showing spherical aberration, astigmatism anddistortion aberration at an intermediate focal position between thewide-angle end and a telephoto end.

FIG. 8 is charts showing spherical aberration, astigmatism anddistortion aberration at the telephoto end.

FIG. 9 shows a third embodiment of a zoom lens of the present inventiontogether with FIGS. 10 to 12, and is a schematic view showing a lensconfiguration.

FIG. 10 is charts showing spherical aberration, astigmatism anddistortion aberration at a wide-angle end.

FIG. 11 is charts showing spherical aberration, astigmatism anddistortion aberration at an intermediate focal position between thewide-angle end and a telephoto end.

FIG. 12 is charts showing spherical aberration, astigmatism anddistortion aberration at the telephoto end.

FIG. 13 shows a fourth embodiment of a zoom lens of the presentinvention together with FIGS. 14 to 16, and is a schematic view showinga lens configuration.

FIG. 14 is charts showing spherical aberration, astigmatism anddistortion aberration at a wide-angle end.

FIG. 15 is charts showing spherical aberration, astigmatism anddistortion aberration at an intermediate focal position between thewide-angle end and a telephoto end.

FIG. 16 is charts showing spherical aberration, astigmatism anddistortion aberration at the telephoto end.

FIG. 17 shows a fifth embodiment of a zoom lens of the present inventiontogether with FIGS. 18 to 20, and is a schematic view showing a lensconfiguration.

FIG. 18 is charts showing spherical aberration, astigmatism anddistortion aberration at a wide-angle end.

FIG. 19 is charts showing spherical aberration, astigmatism anddistortion aberration at an intermediate focal position between thewide-angle end and a telephoto end.

FIG. 20 is charts showing spherical aberration, astigmatism anddistortion aberration at the telephoto end.

FIG. 21 is a block diagram of substantial parts showing an embodiment ofan imaging apparatus of the present invention.

FIG. 22 is a chart in which several glass materials which arecommercially available are distributed with refractive indexes thereofindicated in ordinate and with Abbe numbers thereof indicated inabscissa.

FIG. 23 is a chart in which the several glass materials which arecommercially available are distributed with partial dispersion ratiosthereof indicated in ordinate and with Abbe numbers thereof indicated inabscissa, and a standard line is indicated.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, respective embodiments of a zoom lens of the presentinvention are described with reference to accompanying drawings. FIGS. 1to 4 show a first embodiment, FIGS. 5 to 8 show a second embodiment,FIGS. 9 to 12 show a third embodiment, FIGS. 13 to 16 show a fourthembodiment, and FIGS. 17 to 20 show a fifth embodiment, respectively.

In the description below, “si” denotes an i-th surface from the objectside, “ri” denotes a curvature radius of the surface “si”, “di denotes asurface interval on the optical axis between the i-th surface and ani+1-th surface from the object side, “ni” denotes a refractive index ata line d (wavelength 587.6 nm) of an i-th lens from the object side,“vi” denotes an Abbe number at the line d of the i-th lens from theobject side, “f” denotes a focal length of an entire lens system, “Fno”denotes an open aperture F value, and “ω” denotes a half view angle,respectively.

As shown in FIGS. 1 and 5, zoom lenses 1, 2 according to the first andsecond embodiments are inner focus type zoom lenses having a four-groupconfiguration consisting of a first lens group Gr1 having positiverefractive power, a second lens group Gr2 having negative refractivepower, which is movable in an optical axis direction mainly for zooming(varying power), a third lens group Gr3 having positive refractivepower, and a fourth lens group Gr4 having negative refractive force,which is movable in the optical axis direction for correctingfluctuations in focal position during zooming and for focusing, whichlens groups are arrayed in order from the object side.

Furthermore, as shown in FIGS. 9, 13 and 17, zoom lenses 3, 4 accordingto the third, fourth and fifth embodiments are inner focus type zoomlenses having a five-group configuration consisting of a first lensgroup Gr1 having positive refractive power, a second lens group Gr2having negative refractive power, which is movable in an optical axisdirection mainly for zooming (varying power), a third lens group Gr3having positive refractive power, a fourth lens group Gr4 havingnegative refractive force, which is movable in the optical axisdirection for correcting fluctuations in focal position during zoomingand for focusing, and a fifth lens group Gr5 having positive refractivepower, which lens groups are arrayed in order from the object side.

The first lens group Gr1 has at least a concave lens, a convex lens, anda triple-cemented lens in which special low-dispersion glass issandwiched in the middle, which lenses are arrayed in order from theobject side.

A detailed description of the zoom lenses 1, 2 according to the firstand second embodiments is first given.

In the zoom lenses 1 and 2 according to the first and secondembodiments, the first lens group Gr1 is composed of four-group, sixlenses consisting of a first lens L1 of a concave meniscus lens whoseconvex surface faces the object side, a second lens L2 of a convex lens,a triple-cemented lens T1 made of a third lens L3 of a concave meniscuslens whose convex surface faces the object side, a fourth lens L4 of aconvex lens and a fifth lens L5 of a concave meniscus lens whose concavesurface faces the object side, and a sixth lens L6 of a convex lens,which lenses are arrayed in order from the object side.

The second lens group Gr2 is composed of two-group, three lensesconsisting of a seventh lens L7 of a concave lens, and a cemented lensT3 made of an eighth lens L8 of a concave lens and a ninth lens L9 of aconvex lens, which lenses are arrayed in order form the object side.

The configuration of the lens groups of the third lens group Gr3 andlater differs between the zoom lens 1 according to the first embodimentand the zoom lens 2 according to the second embodiment.

In the zoom lens 1 according to the first embodiment, the third lensgroup Gr3 is composed of a tenth lens L10 of a convex lens, and thefourth lens group Gr4 is composed of a triple-cemented lens T7 made ofan eleventh lens L11 of a convex lens, a twelfth lens L12 of a concavelens and a thirteenth lens L13 of a convex lens.

In the zoom lens 2 according to the second embodiment, the third lensGr3 is composed of two-group, three lenses consisting of a tenth lensL10 of a convex lens and a cemented lens T8 made of an eleventh lens L11of a convex lens and a twelfth lens L12 of a concave lens, and thefourth lens group Gr4 is composed of a thirteenth lens L13, which lensesare arrayed in order from the object side.

In the zoom lenses 1, 2 according to the first and second embodiments,the first lens group Gr1 is characterized by having at least one concavelens and one convex lens. On the wide-angle side, by the concave lens(the first lens L1) and the convex lens (the second lens L2) arrayed inorder from the object side, a wide angle of view can be achieved, andthe correction of curved field can be facilitated. Furthermore, on thetelephoto side, since the first lens group Gr1 has positive refractivepower, spherical aberration on the lower side is easily caused. However,an action of the concave lens L2 arranged closer to the objectfacilitates the correction of this spherical aberration.

It is publicly known that using a material having a large Abbe numberand abnormal partial dispersibility for a convex lens in a front groupof a lens system is effective to the correction of chromatic aberrationand secondary spectrum at a telephoto end.

However, in the zoom lenses 1 and 2, at the telephoto end, an incidentlight flux is designed to expand most by the triple-cemented lens T1.Accordingly, since the chromatic aberration at the telephoto end issubject to the configuration of the triple-cemented lens T1, materialsof the triple-cemented lens T1 need to be suitable for the correction ofthe secondary spectrum in a general telephoto lens, that is, thetriple-cemented lens T1 has a material composition satisfying thefollowing conditional formulae.n1−n2>0.3  (1)|v1−v2|>40  (2)|n2−n3|<0.1  (3)v23>80  (4)ΔP23>0.03  (5)

At this time, refractive indexes at a line C, a line d, a line F and aline g are nC, nd, nF and ng, respectively,

nx: the refractive index nd at the line d of a lens Ax (an x-th lensfrom the object side among the triple-cemented lens, hereinafter, thisis the same),

vx: an Abbe number vd=(nd−1)/(nF−nC) at the line d of the lens Ax, and

Px: a partial dispersion ratio P=(ng−nF)/(nF−nC) of the lens Ax.

Furthermore, if a convex lens A2 (the fourth lens L4) and a secondconcave lens A3 (the fifth lens L5) of the triple-cemented lens T1 areassumed to be a thin and closely-attached system, the convex lens A2 andthe second concave lens A3 can be considered to be one virtual glassmaterial A23.

Accordingly, with fx: a focal length of the lens Ax, a focal length ofthe glass material A23 is obtained by the following formula (6) and adispersion value is obtained by the subsequent formula (7),1/f23=1/f2+1/f3  (6)1/f23·v23=1/f2·v2+1/f3·v3  (7)and by using the above-mentioned values, a partial dispersion ratio P23is obtained by the following formula (8).P23=(f2·v2·P3+f3·v3·P2)/(f2·v2+f3·v3)  (8)

If in FIG. 22, with an Abbe number v indicated in abscissa and arefractive index n indicated in ordinate, and in FIG. 23, with the Abbenumber v indicated in abscissa and a partial dispersion ratio Pindicated in ordinate, part of glass materials produced by HOYACORPORATION are shown, and if a standard line passing glass materials C7and F2 is Pbase in FIG. 23,

-   -   Pbase=−0.00174906×v23+0.64662907        and at this time,    -   ΔP23=P23−Pbase

Then, glass materials of the convex lens A2 (the fourth lens L4) and thesecond concave lens A3 (the fifth lens L5) are arbitrarily selected fromthe glass materials shown in FIG. 23, and when the inclination of a lineconnecting these two glass materials is gentler than that of thestandard line Pbase, secondary spectrum is reduced as compared with acase where achromatism is performed on the standard line Pbase.

The conditional formulae (1) and (2) express primary achromatismconditions, and requisites for correcting primary chromatic aberrationon the telephoto side. If the conditional formulae (1) and (2) are notsatisfied, the chromatic aberration at the telephoto end becomesremarkable, so that the high variable power rate of 40 times cannot berealized.

In the zoom lenses 1 and 2, it is assumed that the speciallow-dispersion glass, for example, FCD1 or FCD10 is used for the lens A2(the fourth lens L4) in the middle of the triple-cemented lens T1, andin order to satisfy the conditional formulae (1), (2), for a firstconcave lens A1 (the third lens L3), glass materials other than flinttype FDS60, FDS90, TaFD30 and FDS1, for example, are excluded.

The conditional formulae (3), (4), (5) are secondary achromatismconditions and requisites for correcting secondary chromatic aberrationon the telephoto side. When the conditional formula (3) is notsatisfied, it is difficult to correct spherical aberration, comaaberration, and axial chromatic aberration on the telephoto side. Whenthe conditional formulae (4) and (5) are satisfied, the inclination ofthe line connecting the glass materials of the convex lens A2 (thefourth lens L4) and the second concave lens A3 (the fifth lens L5)becomes gentler than the inclination of the standard line Pbase shown inFIG. 23, contributing to a reduction in the secondary spectrum. Forthis, by selecting the glass materials of the convex lens A2 (L4) madeof special low-dispersion glass and the second concave lens A3 (L5) soas to satisfy the conditional formula (3) and |P2−P3|<0.03, a desiredcomposition can be obtained.

In the zoom lenses 1 and 2, it is assumed that FCD1 or FCD10 which isspecial low-dispersion glass is used for the lens A2 (L4) in the middleof the triple-cemented lens T1, and in order to satisfy the conditionalformulae (4) and (5), it is necessary to select the glass materials soas to satisfy the conditional formula (3) and |P2−P3|<0.03. For this, itis necessary to use a glass material which is of crown type and islocated above the standard line Pbase in FIG. 23 for the second concavelens A3 (L5). When the conditional formulae (4) and (5) are notsatisfied, the inclination of the line connecting the glass material ofthe convex lens A2 (L4) and the glass material of the second concavelens A3 (L5) is the same as the inclination of the standard line Pbaseshown in FIG. 23, which makes it difficult to correct the secondaryspectrum.

From the foregoing, the following combinations of the glass materials ofthe respective lenses for composing the triplet-cemented lens T1obtained by attaching the three lenses can be considered. Namely, it canbe considered that for the first concave lens A1 (L3), flint type FDS90or FDS1 is used, for the convex lens A2 (L4), FCD1 or FCD10 of speciallow-dispersion glass is used, and for the second concave lens A3 (L5),BSC7, C3, CF6 or the like which is of crown type and is located abovethe standard line Pbase in FIG. 23 is used.

Here, it should be noted that the special low-dispersion glass is usedfor the convex lens A2 (L4) of the triple-cemented lens T1. Since thespecial low-dispersion glass has a soft quality and low latent flawresistance, latent flaws are easily caused during ultrasonic cleaningperformed in lens manufacturing. However, by sandwiching the speciallow-dispersion glass between the lenses A1 (L3), A3 (L5) made of generalglass from both surfaces thereof, even if some hiatus is caused, it canbe filled with an adhesive agent. Furthermore, the speciallow-dispersion glass has a problem in that due to a large thermalexpansion coefficient, when the lens is heated in vacuum in a vapordeposition process for lens coating and air is caused to flow inimmediately after the vapor deposition, the glass is rapidly cooled bythe air, so that cracks easily occur. However, by adhesive-bonding thelenses made of general glass onto both surfaces of the speciallow-dispersion glass, coating itself becomes unnecessary. For thesereasons, the special low-dispersion glass, which has been unsuitable formass production, can be made excellent in mass productivity by using itin the middle of the triple-cemented lens T1.

The third lens group Gr3 which is a fixed group is a part in which alight flux expands most at the wide-angle end, and thus, a part havingdominant influence on spherical aberration and coma aberration at thewide-angle end. Accordingly, in the zoom lenses 1 and 2, at least one ofrespective surfaces composing the third lens group Gr3 is formed of anaspherical surface, and at the same time, at least one of the surfaceseach formed of the aspherical surface is formed into an asphericalsurface shape which is shallower in effective diameter than a depth of aparaxial spherical surface. Furthermore, in the zoom lens 2, it iseffective that the positive refractive power of the third lens group Gr3is divided and shared in the two lens groups and further in one of thegroups, cemented surfaces having negative refractive power are provided.Therefore, in the zoom lens 2, the third lens group Gr3 is composed ofthe convex lens (the tenth lens L10), and the cemented lens T8 of theconvex lens (the eleventh lens L11) and the concave lens (the twelfthlens L12), thereby suppressing the generation of spherical aberrationand the generation of coma aberration.

With respect to the correction of astigmatism and distortion aberrationat the wide-angle end, in the zoom lenses 1 and 2, at least one ofrespective surfaces composing the fourth lens group Gr4 is formed of anaspherical surface and at the same time, at least one of the surfaceseach formed of the aspherical surface is formed into an asphericalsurface shape which is shallower in effective diameter than a depth of aparaxial spherical surface.

Subsequently, the zoom lenses 3, 4, 5 according to the third, fourth andfifth embodiments are described in detail.

In the zoom lenses 3 and 4 according to the third embodiment and thefourth embodiment, the first lens group Gr1 is composed of six-group,eight lenses consisting of a first lens L1 of a concave meniscus lenswhose convex surface faces the object side, a second lens L2 of a convexlens, a third lens L3 of a concave meniscus lens whose convex surfacefaces the object side, a fourth lens L4 of a convex lens, atriple-cemented lens T1 made of a fifth lens L5 of a concave meniscuslens whose convex surface faces the object side, a sixth lens L6 of aconvex lens and a seventh lens L7 of a concave meniscus lens whoseconcave surface faces the object side, and an eighth lens L8 of a convexlens, which lenses are arrayed in order from the object side.

In the zoom lens 5 according to the fifth embodiment, the first lensgroup Gr1 is composed of five-group, eight lenses consisting of a firstlens L1 of a concave meniscus lens whose convex surface faces the objectside, a second lens L2 of a convex lens, a cemented lens T2 made of athird lens L3 of a concave meniscus lens whose convex surface faces theobject side and a fourth lens L4 of a convex lens, a triple-cementedlens T1 made of a fifth lens L5 of a concave meniscus lens whose convexsurface faces the object side, a sixth lens L6 of a convex lens and aseventh lens L7 of a concave meniscus lens whose concave surface facesthe object side, and an eighth lens L8 of a convex lens, which lensesare arrayed in order from the object side.

In the zoom lenses 4, 5 and 6, the second lens group Gr2 is composed ofthree lenses consisting of a ninth lens L9 of a concave lens, and acemented lens T3 made of a tenth lens L10 of a concave lens and aneleventh lens 11 of a convex lens, which lenses are arrayed in orderfrom the object side.

The third lens group is composed of three lenses consisting of a twelfthlens L12 of a convex lens and a cemented lens T4 made of a thirteenthlens of a concave lens and a fourteenth lens L14 of a convex lens, whichlenses are arrayed in order from the object side.

The fourth lens group Gr4 is composed of three lenses consisting of afifteenth lens L15 of a concave lens and a cemented lens T5 made of asixteenth lens L16 of a concave lens and a seventeenth lens L17 of aconvex lens, which lenses are arrayed in order from the object side.

The fifth lens group Gr5 is composed of three lenses consisting of aneighteenth lens L18 of a convex lens and a cemented lens T6 made of anineteenth lens L19 of a convex lens and a twentieth lens L20 of aconcave lens, which lenses are arrayed in order from the object side.

In addition, the first lens group Gr1 can be divided into a front groupconsisting of the first lens L1 to the third lens L3 which has negativerefractive power and a rear group consisting of the fourth lens L4 tothe eighth lens L8 which has positive refractive power.

The front group of the first lens group Gr1 is characterized by havingat least one concave lens and one convex lens. By using the concave lens(the first lens L1) and the convex lens (the second lens L2) whichlenses are arrayed in order from the object side, at the wide-angle end,the concave lens makes the inclination of a principal ray gentle,thereby facilitating the correction of curved field, and the action ofthe convex lens L2 facilitates the correction of distortion aberration.Furthermore, at the telephoto side, although spherical aberration on thelower side is easily caused because the first lens group Gr1 haspositive refractive power, the action of the concave lens arrangedcloser to the object side facilitates the correction of this sphericalaberration. Moreover, although the front group of the first lens groupGr1 has strong negative refractive power, in order to suppress thegeneration of distortion aberration on the barrel side is suppressed asmuch as possible, the first lens L1 and the third lens L3 are each madeof a concave meniscus lens whose convex surface face the object side,and further since the distortion aberration at the wide-angle end needsto be corrected by positive refractive power, this is corrected by thesecond lens L2 which is a convex lens.

It is publicly known that using a material having a large Abbe numberand abnormal partial dispersibility for the convex lens of the frontgroup in the lens system is effective to the correction of chromaticaberration and the correction of secondary spectrum at the telephotoside.

However, the zoom lenses 3, 4 and 5, an incident light flux is designedto expand most in the triple-cemented lens T1 at the telephoto end.Accordingly, since the chromatic aberration at the telephoto end issubject to the configuration of the triple-cemented lens T1, thematerials of the triple-cemented lens T1 need to be suitable for thecorrection of the secondary spectrum in a general telephoto lens, thatis, the triple-cemented lens T1 need to have a material compositionsatisfying the above-described conditional formulae (1), (2), (3), (4)and (5).

Furthermore, if a convex lens A2 (the sixth lens L6) and a secondconcave lens A3 (the seventh lens L7) of the triple-cemented lens T1 areassumed to be a thin and closely-attached system, the convex lens A2 andthe second concave lens A3 can be considered to be one virtual glassmaterial A23.

Accordingly, a focal length of the virtual glass material A23 isobtained by the formula (6), and a dispersion value is obtained by theformula (7), and by using the values, a partial dispersion ratio P23 isobtained by the formula (8).

As described above, if in FIG. 22, with an Abbe number v indicated inabscissa and a refractive index n indicated in ordinate, and in FIG. 23,with an Abbe number v indicated in abscissa and a partial dispersionratio P indicated in ordinate, part of glass materials produced by HOYACORPORATION are shown, and if the standard line passing the glassmaterials C7 and F2 is Pbase in FIG. 14,

-   -   Pbase=−0.00174906×v23+0.64662907        and at this time,    -   ΔP23=P23−Pbase

Then, the glass materials of the convex lens A2 (the sixth lens L6) andthe second concave lens A3 (the seventh lens L7) are arbitrarilyselected from the glass materials shown in FIG. 23, and when theinclination of a line connecting these two glass materials is gentlerthan that of the standard line Pbase, secondary spectrum is reduced ascompared with a case where achromatism is performed on the standard linePbase.

The conditional formulae (1) and (2), as described above, expressprimary achromatism conditions, and requisites for correcting primarychromatic aberration on the telephoto side. If the conditional formulae(1) and (2) are not satisfied, the chromatic aberration at the telephotoend becomes remarkable, so that the high variable power rate of 40 timescannot be realized.

In the zoom lenses 3, 4 and 5, it is assumed that the speciallow-dispersion glass, for example, FCD1 or FCD10 is used for the lens A2(the sixth lens L6) in the middle of the triple-cemented lens T1, and inorder to satisfy the conditional formulae (1), (2), for a first concavelens A1 (the fifth lens L5), glass materials other than flint typeFDS60, FDS90, TaFD30 and FDS1, for example, are excluded.

The conditional formulae (3), (4), (5), as described above, expresssecondary achromatism conditions and requisites for correcting secondarychromatic aberration on the telephoto side. When the conditional formula(3) is not satisfied, it is difficult to correct the sphericalaberration, coma aberration, and axial chromatic aberration on thetelephoto side. When the conditional formulae (4) and (5) are satisfied,the inclination of the line connecting the glass materials of the convexlens A2 (the sixth lens L6) and the second concave lens A3 (the seventhlens L7) becomes gentler than the inclination of the standard line Pbaseshown in FIG. 23, contributing to a reduction in secondary spectrum. Forthis, by selecting the glass materials of the convex lens A2 (L6) madeof special low-dispersion glass and the second concave lens A3 (L7) soas to satisfy the conditional formula (3) and |P2−P3|<0.03, the desiredcomposition can be obtained. In the zoom lenses 3, 4 and 5, it isassumed that FCD1 or FCD10 which is special low-dispersion glass is usedfor the lens A2 (L6) in the middle of the triple-cemented lens T1, andin order to satisfy the conditional formulae (4) and (5), it isnecessary to select the glass materials so as to satisfy the conditionalformula (3) and |P2−P3|<0.03. For this, it is necessary to use a glassmaterial which is of crown type and is located above the standard linePbase in FIG. 23 for the second concave lens A3 (L7). When theconditional formulae (4) and (5) are not satisfied, the inclination ofthe line connecting the glass material of the convex lens A2 (L6) andthe glass material of the second concave lens A3 (L7) is the same as theinclination of the standard line Pbase shown in FIG. 23, which makes itdifficult to correct the secondary spectrum.

From the foregoing, the following combinations of the glass materials ofthe respective lenses for composing the triplet-cemented lens T1obtained by attaching the three lenses can be considered. Namely, it canbe considered that for the first concave lens A1 (L5), flint type FDS90or FDS1 is used, for the convex lens A2 (L6), FCD1 or FCD10 of speciallow-dispersion glass is used, and for the second concave lens A3 (L7),BSC7, C3, CF6 or the like which is of crown type and is located abovethe standard line Pbase in FIG. 23.

Here, it should be noted that the special low-dispersion glass is usedfor the convex lens A2 (L6) of the triple-cemented lens T1. Since thespecial low-dispersion glass has a soft quality and low latent flawresistance, latent flaws are easily caused during ultrasonic cleaningperformed in lens manufacturing. However, by sandwiching the speciallow-dispersion glass between the lenses A1 (L5), A3 (L7) made of generalglass from both surfaces thereof, even if some hiatus is caused, it canbe filled with an adhesive agent. Furthermore, the speciallow-dispersion glass has a problem in that due to a large thermalexpansion coefficient, when the lens is heated in vacuum in a vapordeposition process for lens coating and air is caused to flow inimmediately after the vapor deposition, the glass is rapidly cooled bythe air, so that cracks easily occur. However, by adhesive-bonding thelenses made of general glass on both surfaces of the speciallow-dispersion glass, coating itself becomes unnecessary. For thesereasons, the special low-dispersion glass, which has been unsuitable formass production, can be made excellent in mass productivity by using itin the middle of the triple-cemented lens T1.

With respect to the correction of spherical aberration and comaaberration at the wide-angle end, in the zoom lenses 3, 4 and 5, atleast one of respective surfaces of the twelfth lens L12 to thefourteenth lens L14 composing the third lens group Gr3 is formed of anaspherical surface and at the same time, at least one of the surfaceseach formed of the aspherical surface is formed into an asphericalsurface shape which is shallower in effective diameter than a depth of aparaxial spherical surface.

The third lens group Gr3 which functions to change a diverged light fluxcoming out of the second lens group Gr2 to a converged light flux andsend it to the fourth lens group Gr4 has strong positive refractivepower and is a part in which the light flux expands most at thewide-angle end, and thus, a part having dominant influence on thespherical aberration and the coma aberration at the wide-angle end.Accordingly, in order to change the diverged light flux to the convergedlight flux moderately, it is effective that the positive refractivepower of the third lens group Gr3 is divided and shared in the two lensgroups and further in one of the groups, cemented surfaces havingnegative refractive power are provided. Therefore, in the zoom lens 3, 4and 5, the third lens group Gr3 is composed of the convex lens (thetwelfth lens L12), and the cemented lens T4 made of the concave lens(the thirteenth lens L13) and the convex lens (the fourteen lens L14),thereby suppressing the generation of spherical aberration and thegeneration of coma aberration.

Further, in order to make assurance double sure, as described above, atleast one of respective surfaces s21 to s25 of the twelfth lens L12 tothe fourteenth lens L14 is formed into an aspherical surface and at thesame time, at least one of the surfaces each formed into the asphericalsurface is formed into an aspherical surface shape which is shallower ineffective diameter than a depth of a paraxial spherical surface.

With respect to the correction of astigmatism and distortion aberrationat the wide-angle end, in the zoom lenses 3, 4 and 5, at least one ofrespective surfaces of the eighteenth lens L18 to the twentieth lens L20composing the fifth lens group Gr5 is formed of an aspherical surfaceand at the same time, at least one of the surfaces each formed of theaspherical surface is formed into an aspherical surface shape which isshallower in effective diameter than a depth of a paraxial sphericalsurface.

A ray height of a principal ray raised outside in the fourth lens groupGr4 becomes higher than a maximum image height in the fifth lens groupGr5, and thus, the principal ray needs to be bent so that an exit pupilis located behind an image surface. Accordingly, in order to bend theprincipal ray moderately, in the fifth lens group Gr5, the positiverefractive power is divided and shared in the two lens groups and in oneof the lens groups, the cemented surfaces having the negative refractivepower are provided. Consequently, the fifth lens group Gr5 is composedof the convex lens (the eighteenth lens L18) and the cemented lens T6made of the convex lens (the nineteenth lens L19) and the concave lens(the twentieth lens L20) to thereby suppress the generation ofastigmatism and distortion aberration.

Furthermore, in order to make assurance double sure, as described above,at least one of respective surfaces s32 to s35 of the eighteenth lensL18 to the twentieth lens L20 is formed into an aspherical surface andat the same time, at least one of the surfaces each formed into theaspherical surface is formed into an aspherical surface shape which isshallower in effective diameter than a depth of a paraxial sphericalsurface.

FIG. 21 is a block diagram showing a configuration example of an imagingapparatus 100 according to the present invention. In FIG. 21, referencenumeral 101 denotes a photographing lens capable of zooming which isprovided with a focus lens 101 a and variator lens 101 b, referencenumeral 102 denotes an imaging element (imaging means) such as CCD,reference numeral 103 denotes image control circuit (image controlmeans) controlling various operations such as correction of an image,reference numeral 104 denotes a first image memory storing image dataobtained from the imaging element 102, and reference numeral 105 denotesa second image memory storing image data with distortion corrected.Reference numeral 106 denotes a data table storing distortion aberrationinformation of the photographing lens 101, and reference numeral 107denotes a zoom switch transforming a direction of zooming by aphotographer into an electrical signal.

For example, the zoom lens 1, 2, 3, 4 or 5 according to each of theabove-mentioned embodiments can be applied to the photographing lens101, and in this case, the focus lens 101 a corresponds to the fourthlens group Gr4, and the variator lens 101 b corresponds to the secondlens group Gr2.

With respect to distortion aberration of the zoom lens 101, a distortionaberration curved line varies in accordance with zooming as shown inFIGS. 2 to 4, FIGS. 6 to 8, FIGS. 10 to 12, FIGS. 14 to 16 and FIGS. 18to 20. Accordingly, the variation in distortion aberration depends on aposition of the variator lens 101 b. In the data table 106, there arestored transformation coordinate coefficients associatingtwo-dimensional position information of the first image memory 104 andthe second image memory 105 at a position where the variator lens 101 bis located. Furthermore, the position of the variator lens 101 b isdemarcated into many positions from the wide-angle end to the telephotoend and the transformation coordinate coefficients corresponding to therespective positions are stored in the data table 106.

When the photographer operates the zoom switch 107 to move the variatorlens 101 b, the image control circuit 103 controls to move the focuslens 101 a for preventing defocusing and receives a transformationcoordinate coefficient corresponding to the position of the variatorlens 101 b from the data table 106. When the position of the variatorlens 101 b does not coincide with any position demarcated in advance, anappropriate transformation coordinate coefficient is obtained byprocessing such as interpolation from a transformation coordinatecoefficient at a near position. While the transformation coordinatecoefficient is a coefficient for moving positions of points on an imagewhich are arranged discretely, for an image between the points arrangeddiscretely, the destination of the movement is obtained by theprocessing such as interpolation. The image control circuit 103 performsvertical and horizontal image moving processing for the information ofthe first image memory 104 obtained from the imaging element 102, basedon this transformation coordinate coefficient to thereby correctdistortion, creates image information with the distortion corrected inthe second image memory 105, and outputs a signal based on the imageinformation created in the second image memory 105, as a video signal.

Subsequently, a description of numeric value examples of the zoom lenses1, 2, 3, 4 and 5 according to the respective embodiments is given. InFIGS. 1, 5, 9, 13 and 17, reference character IR denotes an iris fixedimmediately before the third lens group Gr3 and reference character FLdenotes a filter interposed before an image surface IMG.

The lenses used in the respective embodiments include lenses whose lenssurfaces are each formed of an aspherical surface. If a depth of theaspherical surface is “x” and a height from the optical axis is “H”, theaspherical surface shape is defined by the following formula.x=H2/ri·{1+(1−H2/ri2)1/2}+A4·H4+A6·H6+A8·H8+A10·H10wherein A4, A6, A8 and A10 are 4th-order, 6th-order 8th-order and10th-order aspherical surface coefficients, respectively.

In table 1, respective values in a numeric value example of the zoomlens 1 according to the first embodiment are shown. TABLE 1 si ri di nivi s1 r1 = 50.4272 d1 = 0.7143 n1 = 1.58913 v1 = 61.2526 s2 r2 = 23.1849d2 = 3.8095 s3 r3 = 34.5194 d3 = 1.4285 n2 = 1.65844 v2 = 50.8546 s4 r4= −78.6878 d4 = 0.0476 s5 r5 = 16.8966 d5 = 0.4520 n3 = 1.84666 v3 =23.7848 s6 r6 = 11.4598 d6 = 1.9047 n4 = 1.45650 v4 = 90.2697 s7 r7 =−31.6475 d7 = 0.3809 n5 = 1.51680 v5 = 64.1983 s8 r8 = 164.8605 d8 =0.0476 s9 r9 = 11.8892 d9 = 1.2455 n6 = 1.69350 v6 = 53.2008 s10 r10 =19.4598 d10 = 0.3809 s11 r11 = 34.0912 d11 = 0.3140 n7 = 1.88300 v7 =40.8054 s12 r12 = 3.2540 d12 = 1.4285 s13 r13 = −5.0131 d13 = 0.1905 n8= 1.77250 v8 = 49.6243 s14 r14 = 3.6344 d14 = 0.8444 n9 = 1.84666 v9 =23.7848 s15 r15 = −64.4255 d15 = 14.3532 s16 r16 = ∞ d16 = 0.6905 Iriss17 r17 = 4.7618 d17 = 0.8070 n10 = 1.58313 v10 = 59.4596 s18 r18 =13.4520 d18 = 3.3226 s19 r19 = 5.8528 d19 = 0.5562 n11 = 1.58313 v11 =59.4596 s20 r20 = −9.7289 d20 = 0.2143 n12 = 1.84666 v12 = 23.7848 s21r21 = 5.8251 d21 = 0.7084 n13 = 1.72342 v13 = 37.9941 s22 r22 = −5.7626d22 = 1.7930 s23 r23 = ∞ d23 = 1.5178 n14 = 1.51680 v14 = 64.1983 s24r24 = ∞ d24 = 0.5714 s25 r25 = ∞ d25 = 0.2048 n15 = 1.55232 v15 =63.4241 s26 r26 = ∞ d26 = 0.3809 s27 r27 = ∞ d27 = 0.3571 n16 = 1.55671v16 = 58.5624 s28 r28 = ∞ d28 = 0.3851

As shown in the above table 1, surface intervals d10, d15, d18 and d22are variable in accordance with operation involved with the zooming andfocusing of the zoom lens 1. Respective values at the wide-angle end(f=1.00), the telephoto end (f=39.00) and the intermediate focalposition (f=19.5) between the wide-angle end and the telephoto end areshown in table 2. TABLE 2 Focal Length (f) 1.00 19.50 39.00 Angle ofView (2ω) 67.5 3.14 1.55 d10 0.38095 13.06149 14.35356 d15 14.353191.67256 0.38095 d18 3.32261 1.73878 4.18323 d22 1.79302 3.37693 0.93203

Furthermore, in the first lens group Gr1, the third lens group Gr3 andthe fourth lens group Gr4, a surface s9 of the sixth lens L6, surfacess17 and s18 of the tenth lens L10, and a surface s19 of the eleventhlens L11 are each formed into an aspherical surface. In table 3, the4th-order, 6th-order, 8th-order and 10th-order aspherical surfacecoefficients A4, A6, A8 and A10 of the surfaces s9, s17, s18 and s19 areshown. TABLE 3 ASPHERICAL SURFACE COEFFICIENT A4 A6 A8 A10 s9  1.27E−05 9.63E−08  2.87E−09 −4.03E−011 s17 −1.69E−03 −1.32E−03 −6.14E−05 1.72E−05 s18 −8.08E−04 −1.71E−03  2.71E−05  1.71E−05 s19 −4.19E−03 1.07E−04 −1.58E−04  3.44E−05

Reference character E in the above table 3 indicates an exponentialnotation with a base 10 (similar in tables 7, 11, 15, and 19 describedlater).

Table 4 shows values of the conditional formulae (1) to (5) and valuesof f, Fno and 2ω of the zoom lens 1. TABLE 4 No. of Formula (1) n1-n20.3901 (2) |v1-v2| 66.49 (3) |n2-n3| 0.0603 (4) v23 117.4 (5) ΔP230.0925 f  1.0˜39.00 Fno 1.69˜4.33 2ω 1.54˜67.5

FIGS. 2 to 4 show spherical aberration charts, astigmatism charts anddistortion aberration charts at the wide-angle end, the intermediatefocal position between the wide-angle end and the telephoto end, and thetelephoto end of the zoom lens 1, respectively. In each of the sphericalaberration charts, a solid line denotes a value at a line e, a brokenline denotes a value at the line C (wavelength 656.3 nm), a dashed linedenotes a value at the line g (wavelength 435.8 nm), and in each of theastigmatism charts, a solid line denotes a value in a sagittal imagesurface, and a broken line denotes a value in a meridional imagesurface.

Table 5 shows respective values in a numeric value example of the zoomlens 2 according to the second embodiment. TABLE 5 si ri di ni vi s1 r1= 43.1956 d1 = 1.1017 n1 = 1.58913 v1 = 61.2526 s2 r2 = 40.0010 d2 =4.0001 s3 r3 = −457.8264 d3 = 1.5000 n2 = 1.65844 v2 = 50.8546 s4 r4 =−56.2690 d4 = 0.9000 s5 r5 = 14.2791 d5 = 0.9000 n3 = 1.92286 v3 =20.8835 s6 r6 = 11.5003 d6 = 2.9194 n4 = 1.45650 v4 = 90.2697 s7 r7 =−21.2417 d7 = 0.4000 n5 = 1.51680 v5 = 64.1983 s8 r8 = 595.1446 d8 =0.0500 s9 r9 = 12.1720 d9 = 1.1456 n6 = 1.71300 v6 = 53.9389 s10 r10 =14.6323 d10 = 0.4000 s11 r11 = 20.4083 d11 = 0.2250 n7 = 1.88300 v7 =40.8054 s12 r12 = 3.1099 d12 = 1.5000 s13 r13 = −3.1147 d13 = 0.2000 n8= 1.77250 v8 = 49.6243 s14 r14 = 3.5001 d14 = 0.7220 n9 = 1.84666 v9 =23.7848 s15 r15 = −27.8718 d15 = 15.6859 s16 r16 = ∞ d16 = 0.7250 Iriss17 r17 = 5.6740 d17 = 0.7000 n10 = 1.58313 v10 = 59.4596 s18 r18 =−10.6219 d18 = 0.4000 s19 r19 = 8.3468 d19 = 1.0000 n11 = 1.51680 v11 =64.1983 s20 r20 = ∞ d20 = 0.6362 n12 = 1.84666 v12 = 23.7848 s21 r21 =5.7586 d21 = 4.6364 s22 r22 = 4.4476 d22 = 0.7570 n13 = 1.48749 v13 =70.4412 s23 r23 = −6.2578 d23 = 0.4274 s24 r24 = ∞ d24 = 1.5937 n14 =1.51680 v14 = 64.1983 s25 r25 = ∞ d25 = 0.6000 s26 r26 = ∞ d26 = 0.2150n15 = 1.55232 v15 = 63.4241 s27 r27 = ∞ d27 = 0.4000 s28 r28 = ∞ d28 =0.3750 n16 = 1.55671 v16 = 58.5624 s29 r29 = ∞ d29 = 0.398199

As shown in the above table 5, surface intervals d10, d15, d21 and d23are variable in accordance with operation involved with the zooming andfocusing of the zoom lens 2. Respective values of d10, d15, d21 and d23at the wide-angle end (f=1.00), the telephoto end (f=40.00) and theintermediate focal position (f=20.00) between the wide-angle end and thetelephoto end are shown in table 6. TABLE 6 Focal Length (f) 1.00 20.0040.00 Angle of View (2ω) 69.2 3.24 1.60 d10 0.40001 14.20236 15.68574d15 15.68586 1.8835 0.40001 d21 4.6364 0.8516 1.93045 d23 0.427374.21218 3.13345

Furthermore, in the first lens group Gr1, the third lens group Gr3 andthe fourth lens group Gr4, a surface s10 of the sixth lens L6, surfacess17 and s18 of the tenth lens L10, and surfaces s21, 23 of thethirteenth lens L13 are each formed into an aspherical surface. In table7, the 4th-order, 6th-order, 8th-order and 10th-order aspherical surfacecoefficients A4, A6, A8 and A10 of the surfaces s10, s17, s18, s21 ands23 are shown. TABLE 7 ASPHERICAL SURFACE COEFFICIENT A4 A6 A8 A10 s9 1.20E−06 −1.52E−07  9.54E−09 −1.70E−10 s17  5.34E−04 −3.68E−04 1.36E−04  1.71E−05 s18  2.33E−03 −4.69E−04  1.88E−04  1.04E−05 s22−5.42E−04  4.06E−05 −1.81E−04  1.09E−04 s23  3.35E−03 −7.96E−05−1.13E−04  9.91E−05

Table 8 shows values of the conditional formulae (1) to (5) and valuesof f, Fno and 2ω of the zoom lens 2. TABLE 8 No. of Formula (1) n1-n220.4664 (2) |v1-v2| 69.39 (3) |n2-n3| 0.0603 (4) v23 173.6 (5) ΔP230.1901 f  1.0˜40.00 Fno 2.22˜4.00 2ω  1.6˜69.2

FIGS. 6 to 8 show spherical aberration charts, astigmatism charts anddistortion aberration charts at the wide-angle end, the intermediatefocal position between the wide-angle end and the telephoto end, and thetelephoto end of the zoom lens 2, respectively. In each of the sphericalaberration charts, a solid line denotes a value at the line e, a brokenline denotes a value at the line C (wavelength 656.3 nm), a dashed linedenotes a value at the line g (wavelength 435.8 nm), and in each of theastigmatism charts, a solid line denotes a value in the sagittal imagesurface, and a broken line denotes a value in the meridional imagesurface.

Table 9 shows respective values in a numeric value example of the zoomlens 3 according to the third embodiment. TABLE 9 si ri di ni vi s1 r1 =135.0548 d1 = 1.6367 n1 = 1.58913 v1 = 61.3 s2 r2 = 21.9858 d2 = 6.3098s3 r3 = 87.9983 d3 = 2.7379 n2 = 1.65844 v2 = 50.9 s4 r4 = −151.9657 d4= 0.2842 s5 r5 = 54.8202 d5 = 1.0690 n3 = 1.69680 v3 = 55.5 s6 r6 =27.0625 d6 = 6.3819 s7 r7 = 55.0902 d7 = 2.9200 n4 = 1.48749 v4 = 70.4s8 r8 = −47.7401 d8 = 0.3016 s9 r9 = 22.1424 d9 = 0.9025 n5 = 1.84666 v5= 23.8 s10 r10 = 15.9194 d10 = 5.1095 n6 = 1.45650 v6 = 90.3 s11 r11 =−22.6561 d11 = 0.6837 n7 = 1.51680 v7 = 64.2 s12 r12 = −124.6613 d12 =0.3247 s13 r13 = 15.9313 d13 = 2.3449 n8 = 1.48749 v8 = 70.4 s14 r14 =−183.8100 d14 = 0.5368 s15 r15 = 91.4222 d15 = 0.2735 n9 = 1.88300 v9 =40.8 s16 r16 = 3.6956 d16 = 1.0809 s17 r17 = −4.6904 d17 = 0.9454 n10 =1.77250 v10 = 49.6 s18 r18 = 3.3394 d18 = 1.6882 n11 = 1.84666 v11 =23.8 s19 r19 = 45.5199 d19 = 14.8645 s20 r20 = ∞ d20 = 0.6047 Iris s21r21 = 11.1968 d21 = 1.3505 n12 = 1.58913 v12 = 61.3 s22 r22 = −10.4032d22 = 0.2665 s23 r23 = 11.0257 d23 = 0.5414 n13 = 1.84666 v13 = 23.8 s24r24 = 5.2712 d24 = 1.3392 n14 = 1.58913 v14 = 61.3 s25 r25 = −13.1584d25 = 0.4727 s26 r26 = −12.2901 d26 = 0.4840 n15 = 1.80420 v15 = 46.5s27 r27 = 11.4654 d27 = 0.6227 s28 r28 = −14.1912 d28 = 1.4856 n16 =1.64769 v16 = 33.8 s29 r29 = 4.9588 d29 = 1.4856 n17 = 1.84666 v17 =23.8 s30 r30 = 165.9091 d30 = 6.8242 s31 r31 = 13.0236 d31 = 1.5531 n18= 1.48749 v18 = 70.4 s32 r32 = −8.8958 d32 = 0.3449 s33 r33 = 5.1931 d33= 2.0490 n19 = 1.58913 v19 = 61.3 s34 r34 = −4.9541 d34 = 0.7020 n20 =1.84666 v20 = 23.8 s35 r35 = −146.0034 d35 = 1.2800 s36 r36 = ∞ d36 =1.6731 nFL = 1.51680 vFL = 64.2 Filter s37 r37 = ∞ Filter

As shown in the above table 9, surface intervals d14, d19, d25 and d30are variable in accordance with operation involved with the zooming andfocusing of the zoom lens 3. Respective values of d14, d19, d25 and d30at the wide-angle end (f=1.00), the telephoto end (f=39.02) and theintermediate focal position (f=17.45) between the wide-angle end and thetelephoto end are shown in table 10. TABLE 10 Focal Length (f) 1.0017.45 39.02 Angle of View (2ω) 82.95 5.71 2.50 d14 0.5368 12.868814.1923 d19 14.8645 2.5320 1.2091 d25 0.4727 5.5619 3.5454 d30 6.82421.7355 3.7528

Furthermore, in the third lens group Gr3 and the fifth lens group Gr5, asurface s21 of the thirteenth lens L13, a surface s33 of the nineteenthlens L19 are each formed into an aspherical surface. In table 11, the4th-order, 6th-order, 8th-order and 10th-order aspherical surfacecoefficients A4, A6, A8 and A10 of the surfaces s21 and s33 are shown.TABLE 11 ASPHERICAL SURFACE COEFFICIENT A4 A6 A8 A10 s21 −6.270E−04−1.815E−05 3.070E−06 −1.531E−07 s33  1.307E−04 −4.900E−05 1.077E−05−2.187E−07

Table 12 shows values of the conditional formulae (1) to (5) and valuesof f, Fno and 2ω of the zoom lens 1. TABLE 12 No. of Formula (1) n1-n20.3902 (2) |v1-v2| 66.5 (3) |n2-n3| 0.0603 (4) v23 119.1 (5) ΔP23 0.0955f  1.0˜39.02 Fno 1.87˜3.50  2ω 2.50˜82.95

FIGS. 10 to 12 show spherical aberration charts, astigmatism charts anddistortion aberration charts at the wide-angle end, the intermediatefocal position between the wide-angle end and the telephoto end, and thetelephoto end of the zoom lens 1, respectively. In each of the sphericalaberration charts, a solid line denotes a value at the line e, a brokenline denotes a value at the line C (wavelength 656.3 nm), a dashed linedenotes a value at the line g (wavelength 435.8 nm), and in each of theastigmatism charts, a solid line denotes a value in the sagittal imagesurface, and a broken line denotes a value in the meridional imagesurface.

Table 13 shows respective values in a numeric value example of the zoomlens 4 according to the fourth embodiment. TABLE 13 si ri di ni vi s1 r1= 66.2882 d1 = 1.6539 n1 = 1.58913 v1 = 61.3 s2 r2 = 20.6541 d2 = 6.4156s3 r3 = 49.1034 d3 = 3.3840 n2 = 1.65844 v2 = 50.9 s4 r4 = −572.0262 d4= 0.2347 s5 r5 = 58.5826 d5 = 1.0650 n3 = 1.6980 v3 = 55.5 s6 r6 =24.3020 d6 = 5.8909 s7 r7 = 46.5948 d7 = 3.3143 n4 = 1.48749 v4 = 70.4s8 r8 = −66.8306 d8 = 0.3892 s9 r9 = 24.7720 d9 = 0.5195 n5 = 1.84666 v5= 23.8 s10 r10 = 16.7406 d10 = 5.3035 n6 = 1.49700 v6 = 81.6 s11 r11 =−22.2555 d11 = 0.5454 n7 = 1.51680 v7 = 64.2 s12 r12 = −115.7020 d12 =0.2226 s13 r13 = 15.1221 d13 = 2.2851 n8 = 1.48749 v8 = 70.4 s14 r14 =−251.5416 d14 = 0.4697 s15 r15 = −176.6693 d15 = 0.2684 n9 = 1.88300 v9= 40.8 s16 r16 = 3.7243 d16 = 1.0796 s17 r17 = −4.9431 d17 = 0.8723 n10= 1.77250 v10 = 49.6 s18 r18 = 3.1824 d18 = 1.5335 n11 = 1.84666 v11 =23.8 s19 r19 = 42.0484 d19 = 14.5700 s20 r20 = ∞ (Iris) d20 = 0.6009 s21r21 = 10.9772 d21 = 1.3420 n12 = 1.58913 v12 = 61.3 s22 r22 = −10.1735d22 = 0.1715 s23 r23 = 12.1984 d23 = 0.5412 n13 = 1.84666 v13 = 23.8 s24r24 = 5.2935 d24 = 1.3420 n14 = 1.58913 v14 = 61.3 s25 r25 = −11.5611d25 = 0.4760 s26 r26 = −11.1945 d26 = 0.5625 n15 = 1.80420 v15 = 46.5s27 r27 = 12.9747 d27 = 0.7027 s28 r28 = −9.2151 d28 = 1.4091 n16 =1.64769 v16 = 33.8 s29 r29 = 5.1631 d29 = 1.4091 n17 = 1.84666 v17 =23.8 s30 r30 = −46.6994 d30 = 7.1656 s31 r31 = 12.3391 d31 = 1.5433 n18= 1.48749 v18 = 70.4 s32 s32 = −10.7894 d32 = 0.5325 s33 s33 = 5.2113d33 = 2.2467 n19 = 1.58913 v19 = 61.3 s34 s34 = −4.2705 d34 = 0.6855 n20= 1.84666 v20 = 23.8 s35 s35 = −31.8581 d35 = 1.2719 s36 s36 = ∞(Filter) d36 = 1.6625 nFL = 1.51680 vFL = 64.2 s37 s37 = ∞ (Filter) d37= 0.7970 0.0000

As shown in the above table 13, surface intervals d14, d19, d25 and d30are variable in accordance with operation involved with the zooming andfocusing of the zoom lens 4. Respective values of d14, d19, d25 and d30at the wide-angle end (f=1.00), the telephoto end (f=39.13) and theintermediate focal position (f=19.56) between the wide-angle end and thetelephoto end are shown in table 14. TABLE 14 Focal Length (f) 1.0019.56 39.13 Angle of View (2ω) 82.21 5.08 2.46 d14 0.5368 12.868814.1923 d19 14.8645 2.5320 1.2091 d25 0.4727 5.5619 3.5454 d30 6.82421.7355 3.7528

Furthermore, in the third lens group Gr3 and the fifth lens group Gr5, asurface s21 of the thirteenth lens L13, a surface s33 of the nineteenthlens L19 are each formed into an aspherical surface. In table 15, the4th-order, 6th-order, 8th-order and 10th-order aspherical surfacecoefficients A4, A6, A8 and A10 of the surfaces s21 and s33 are shown.TABLE 15 ASPHERICAL SURFACE COEFFICIENT A4 A6 A8 A10 s21 −6.546E−04−2.577E−05  4.316E−06 −2.326E−07 s33  1.882E−04  1.641E−05 −1.887E−06 1.300E−06

Table 16 shows values of the conditional formulae (1) to (5) and valuesof f, Fno and 2ω of the zoom lens 4. TABLE 16 No. of Formula (1) n1-n20.3497 (2) |v1-v2| 57.8 (3) |n2-n3| 0.0198 (4) v23 87.8 (5) ΔP23 0.0396f  1.0˜39.02 Fno 1.88˜3.00  2ω 2.45˜83.03

FIGS. 14 to 16 show spherical aberration charts, astigmatism charts anddistortion aberration charts at the wide-angle end, the intermediatefocal position between the wide-angle end and the telephoto end, and thetelephoto end of the zoom lens 4, respectively. In each of the sphericalaberration charts, a solid line denotes a value at the line e, a brokenline denotes a value at the line C (wavelength 656.3 nm), a dashed linedenotes a value at the line g (wavelength 435.8 nm), and in each of theastigmatism charts, a solid line denotes a value in the sagittal imagesurface, and a broken line denotes a value in the meridional imagesurface.

Table 17 shows respective values in a numeric value example of the zoomlens 5 according to the fifth embodiment. TABLE 17 si ri di ni vi s1 r1= 138.4722 d1 = 1.8107 n1 = 1.58913 v1 = 61.3 s2 r2 = 22.4749 d2 =9.5463 s3 r3 = 204.2751 d3 = 4.7628 n2 = 1.65844 v2 = 50.9 s4 r4 =−77.7380 d4 = 6.0572 s5 r5 = 41.8463 d5 = 0.8308 n3 = 1.88300 v3 = 40.8s6 r6 = 21.4914 d6 = 3.7774 n4 = 1.48749 v4 = 70.4 s7 r7 = −88.72l6 d7 =0.0692 s8 r8 = 23.0428 d8 = 0.6777 n5 = 1.84666 v5 = 23.8 s9 r9 =17.7950 d9 = 4.0167 n6 = 1.45650 v6 = 90.3 s10 r10 = −30.0894 d10 =0.4154 n7 = 1.51680 v7 = 64.2 s11 r11 = −1498.1836 d11 = 0.0692 s12 r12= 17.1194 d12 = 2.3660 n8 = 1.48749 v8 = 70.4 s13 r13 = −159.8185 d13 =0.4847 s14 r14 = 61.0411 d14 = 0.2769 n9 = 1.88300 v9 = 40.8 s15 r15 =3.8574 d15 = 1.2958 s16 r16 = −5.0162 d16 = 1.0385 n10 = 1.77250 v10 =49.6 s17 r17 = 3.5572 d17 = 1.5652 n11 = 1.84666 v11 = 23.8 s18 r18 =49.6140 d18 = 15.8004 s19 r19 = ∞ d19 = 0.6200 Iris s20 r20 = 10.7776d20 = 2.1463 n12 = 1.58913 v12 = 61.3 s21 r21 = −13.2443 d21 = 0.2769s22 r22 = 12.0398 d22 = 1.1230 n13 = 1.84666 v13 = 23.8 s23 r23 = 5.2197d23 = 1.4341 n14 = 1.58913 v14 = 61.3 s24 r24 = −11.6001 d24 = 0.4847s25 r25 = −15.6400 d25 = 0.2769 n15 = 1.80420 v15 = 46.5 s26 r26 =15.5021 d26 = 0.2883 s27 r27 = −28.0035 d27 = 0.2769 n16 = 1.64769 v16 =33.8 s28 r28 = 4.1174 d28 = 0.6246 n17 = 1.84666 v17 = 23.8 s29 r29 =16.4185 d29 = 6.5532 s30 r30 = 14.9482 d30 = 0.9614 n18 = 1.48749 v18 =70.4 s31 r31 = −10.0348 d31 = 0.0692 s32 r32 = 4.4209 d32 = 1.5644 n19 =1.58913 v19 = 61.3 s33 r33 = −7.2877 d33 = 0.2769 n20 = 1.84666 v20 =23.8 s34 r34 = 125.4468 d34 = 1.3124 s35 r35 = ∞ d35 = 1.7154 nFL =1.51680 vFL = 64.2 Filter s36 r36 = ∞ Filter

As shown in the above table 17, the surface intervals d13, d18, d24 andd29 are variable in accordance with operation involved with the zoomingand focusing of the zoom lens 5. Respective values of d13, d18, d24 andd29 at the wide-angle end (f=1.00), the telephoto end (f=40.08) and theintermediate focal position (f=20.01) between the wide-angle end and thetelephoto end are shown in table 18. TABLE 18 Focal Length (f) 1.00 20.140.08 Angle of View (2ω) 87.93 5.71 2.51 d14 0.4847 13.8656 15.5227 d1815.8004 2.4194 0.7616 d24 0.4847 5.8630 0.6428 d29 6.5532 1.1770 6.4017

Furthermore, in the third lens group Gr3 and the fifth lens group Gr5, asurface s20 of the thirteenth lens L13, a surface s32 of the nineteenthlens L19 are each formed into an aspherical surface. In table 19, the4th-order, 6th-order, 8th-order and 10th-order aspherical surfacecoefficients A4, A6, A8 and A10 of the surfaces s20 and s32 are shown.TABLE 19 ASPHERICAL SURFACE COEFFICIENT A4 A6 A8 A10 s20 −5.873E−04−1.478E−05 1.957E−06 −7.235E−08 s32  1.087E−04 −1.617E−04 3.288E−05−2.183E−06

Table 20 shows values of the conditional formulae (1) to (5) and valuesof f, Fno and 2ω of the zoom lens 5. TABLE 20 No. of Formula (1) n1-n20.3902 (2) |v1-v2| 66.5 (3) |n2-n3| 0.0603 (4) v23 128.7 (5) ΔP23 0.1122f  1.0˜40.08 Fno 1.82˜3.41 2ω 2.51˜87.9

FIGS. 18 to 20 show spherical aberration charts, astigmatism charts anddistortion aberration charts at the wide-angle end, the intermediatefocal position between the wide-angle end and the telephoto end, and thetelephoto end of the zoom lens 5, respectively. In each of the sphericalaberration charts, a solid line denotes a value at the line e, a brokenline denotes a value at the line C (wavelength 656.3 nm), a dashed linedenotes a value at the line g (wavelength 435.8 nm), and in each of theastigmatism charts, a solid line denotes a value in the sagittal imagesurface, and a broken line denotes a value in the meridional imagesurface.

As described above, the present invention can provide a zoom lens havinga zoom ratio of about 40 times which can cover from a super wide-anglearea to a super telephoto area with angles of view of not less than 67degrees at a wide-angle end and not more than 1.6 degrees at a telephotoend, while favorably correcting various aberrations, and further whichis excellent in mass productivity, and in particular to a zoom lenspreferable for a video camera for people's livelihood, and an imagingapparatus using the zoom lens.

The shapes of the respective parts and numeric values shown in theabove-described respective embodiments show only examples for theembodiments when carrying out the present invention, and the technicalscope of the present invention should not be restrictively construed bythese.

INDUSTRIAL APPLICABILITY

The zoom lens according to the present invention covers from super wideangle to super telephoto while favorably correcting various aberrationsand further, it is excellent in mass productivity, and in particular, itis preferably used as a zoom lens for a video camera for people'slivelihood and used for the video camera.

1. A zoom lens of an inner focus type having four or five lens groups,including at least a first lens group having positive refractive power,a second lens group having negative refractive power, which is movablein an optical axis direction mainly for zooming (varying power), a thirdlens group having positive refractive power, and a fourth lens grouphaving positive or negative refractive power, which is movable in theoptical axis direction for correcting fluctuations in focal positionduring zooming and for focusing, which lens groups are arrayed in orderfrom an object side, characterized in that: said first lens groupcomprises at least a concave lens, a convex lens, and a triple-cementedlens in which a lens made of special low-dispersion glass is sandwichedin the middle, which lenses are arrayed in order from the object side.2. The zoom lens as described in claim 1, characterized in that: saidtriple-cemented lens in said first lens group includes a first concavelens A1, a convex lens A2 formed of special low-dispersion glass and asecond concave lens A3, which lenses are arrayed in order from theobject side, and said first concave lens A1 and said convex lens A2 areformed of materials satisfying the following two conditional formulae(1) and (2):n1−n2>0.3  (1)|v1−v2|>40  (2) wherein refractive indexes at a line C, a line d, a lineF and a line g are nC, nd, nF and ng, respectively, and nx is arefractive index nd at the line d of a lens Ax (an xth lens from theobject side among the triple-cemented lens, hereinafter, this is thesame), and vx is an Abbe number vd=(nd−1)/(nF−nC) at the line d of thelens Ax.
 3. The zoom lens as described in claim 1, characterized inthat: said triple-cemented lens in said first lens group includes afirst concave lens A1, a convex lens A2 formed of special low-dispersionglass and a second concave lens A3, which lenses are arrayed in orderfrom the object side, and said convex lens A2 and said second concavelens A3 are formed of materials satisfying the following threeconditional formulae (3), (4), and (5):|n2−n3|<0.1  (3)v23>80  (4)ΔP23>0.03  (5) wherein refractive indexes at a line C, a line d, a lineF and a line g are nC, nd, nF and ng, respectively, and nx is arefractive index nd at the line d of a lens Ax (an xth lens from theobject side among the triple-cemented lens, hereinafter, this is thesame), vx is an Abbe number vd=(nd−1)/(nF−nC) at the line d of the lensAx, and Px is a partial dispersion ratio P=(ng−nF)/(nF−nC) of the lensAx.
 4. The zoom lens as described in claim 2, characterized in that:said triple-cemented lens in said first lens group includes a firstconcave lens A1, a convex lens A2 formed of special low-dispersion glassand a second concave lens A3, which lenses are arrayed in order from theobject side, and said convex lens A2 and said second concave lens A3 areformed of materials satisfying the following three conditional formulae(3), (4), and (5):|n2−n3|<0.1  (3)v23>80  (4)ΔP23>0.03  (5) wherein refractive indexes at a line C, a line d, a lineF and a line g are nC, nd, nF and ng, respectively, and nx is arefractive index nd at the line d of a lens Ax (an xth lens from theobject side among the triple-cemented lens, hereinafter, this is thesame), vx is an Abbe number vd=(nd−1)/(nF−nC) at the line d of the lensAx, and Px is a partial dispersion ratio P=(ng−nF)/(nF−nC) of the lensAx.
 5. The zoom lens as described in claim 1, characterized in that:said first lens group comprises a first lens of a concave meniscus lenswhose convex surface faces the object side, a second lens of a convexlens, a triple-cemented lens made of a third lens of a concave meniscuslens whose convex surface faces the object side, a fourth lens of aconvex lens and a fifth lens of a concave meniscus lens whose concavesurface faces the object side, and a sixth lens of a convex lens, whichlenses are arrayed in order from the object side.
 6. The zoom lens asdescribed in claim 2, characterized in that: said first lens groupcomprises a first lens of a concave meniscus lens whose convex surfacefaces the object side, a second lens of a convex lens, a triple-cementedlens made of a third lens of a concave meniscus lens whose convexsurface faces the object side, a fourth lens of a convex lens and afifth lens of a concave meniscus lens whose concave surface faces theobject side, and a sixth lens of a convex lens, which lenses are arrayedin order from the object side.
 7. The zoom lens as described in claim 3,characterized in that: said first lens group comprises a first lens of aconcave meniscus lens whose convex surface faces the object side, asecond lens of a convex lens, a triple-cemented lens made of a thirdlens of a concave meniscus lens whose convex surface faces the objectside, a fourth lens of a convex lens and a fifth lens of a concavemeniscus lens whose concave surface faces the object side, and a sixthlens of a convex lens, which lenses are arrayed in order from the objectside.
 8. The zoom lens as described in claim 4, characterized in that:said first lens group comprises a first lens of a concave meniscus lenswhose convex surface faces the object side, a second lens of a convexlens, a triple-cemented lens made of a third lens of a concave meniscuslens whose convex surface faces the object side, a fourth lens of aconvex lens and a fifth lens of a concave meniscus lens whose concavesurface faces the object side, and a sixth lens of a convex lens, whichlenses are arrayed in order from the object side.
 9. A zoom lens of aninner focus type including a first lens group having positive refractivepower, a second lens group having negative refractive power, which ismovable in an optical axis direction mainly for zooming (varying power),a third lens group having positive refractive power, a fourth lens grouphaving negative refractive power, which is movable in the optical axisdirection for correcting fluctuations in focal position during zoomingand for focusing, and a fifth lens group having positive refractivepower, which lens groups are arrayed in order from an object side,characterized in that: said first lens group comprises a concave lens, aconvex lens, and a triple-cemented lens in which a lens made of speciallow-dispersion glass is sandwiched in the middle, which lenses arearrayed in order from the object side.
 10. The zoom lens as described inclaim 9, characterized in that: said triple-cemented lens in said firstlens group includes a first concave lens A1, a convex lens A2 formed ofspecial low-dispersion glass and a second concave lens A3, which lensesare arrayed in order from the object side, and said first concave lensA1 and said convex lens A2 are formed of materials satisfying thefollowing two conditional formulae (1) and (2):n1−n2>0.3  (1)|v1−v2|>40  (2) wherein refractive indexes at a line C, a line d, a lineF and a line g are nC, nd, nF and ng, respectively, and nx is arefractive index nd at the line d of a lens Ax (an xth lens from theobject side among the triple-cemented lens, hereinafter, this is thesame), and vx is an Abbe number vd=(nd−1)/(nF−nC) at the line d of thelens Ax.
 11. The zoom lens as described in claim 9, characterized inthat: said triple-cemented lens in said first lens group includes afirst concave lens A1, a convex lens A2 formed of special low-dispersionglass and a second concave lens A3, which lenses are arrayed in orderfrom the object side, and said convex lens A2 and said second concavelens A3 are formed of materials satisfying the following threeconditional formulae (3), (4), and (5):|n2−n3|<0.1  (3)v23>80  (4)ΔP23>0.03  (5) wherein refractive indexes at a line C, a line d, a lineF and a line g are nC, nd, nF and ng, respectively, and nx is arefractive index nd at the line d of a lens Ax (an xth lens from theobject side among the triple-cemented lens, hereinafter, this is thesame), vx is an Abbe number vd=(nd−1)/(nF−nC) at the line d of the lensAx, and Px is a partial dispersion ratio P=(ng−nF)/(nF−nC) of the lensAx.
 12. The zoom lens as described in claim 10, characterized in that:said triple-cemented lens in said first lens group includes a firstconcave lens A1, a convex lens A2 formed of special low-dispersion glassand a second concave lens A3, which lenses are arrayed in order from theobject side, and said convex lens A2 and said second concave lens A3 areformed of materials satisfying the following three conditional formulae(3), (4), and (5):|n2−n3|<0.1  (3)v23>80  (4)ΔP23>0.03  (5) wherein refractive indexes at a line C, a line d, a lineF and a line g are nC, nd, nF and ng, respectively, and nx is arefractive index nd at the line d of a lens Ax (an xth lens from theobject side among the triple-cemented lens, hereinafter, this is thesame), vx is an Abbe number vd=(nd−1)/(nF−nC) at the line d of the lensAx, and Px is a partial dispersion ratio P=(ng−nF)/(nF−nC) of the lensAx.
 13. The zoom lens as described in claim 9, characterized in that:said first lens group comprises a first lens of a concave meniscus lenswhose convex surface faces the object side, a second lens of a convexlens, a third lens of a concave meniscus lens whose convex surface facesthe object side, a fourth lens L4 of a convex lens, a triple-cementedlens made of a fifth lens of a concave meniscus lens whose convexsurface faces the object side, a sixth lens of a convex lens and aseventh lens of a concave meniscus lens whose concave surface faces theobject side, and a sixth lens of a convex lens, which lenses are arrayedin order from the object side.
 14. The zoom lens as described in claim10, characterized in that: said first lens group comprises a first lensof a concave meniscus lens whose convex surface faces the object side, asecond lens of a convex lens, a third lens of a concave meniscus lenswhose convex surface faces the object side, a fourth lens L4 of a convexlens, a triple-cemented lens made of a fifth lens of a concave meniscuslens whose convex surface faces the object side, a sixth lens of aconvex lens and a seventh lens of a concave meniscus lens whose concavesurface faces the object side, and an eighth lens of a convex lens,which lenses are arrayed in order from the object side.
 15. The zoomlens as described in claim 11, characterized in that: said first lensgroup comprises a first lens of a concave meniscus lens whose convexsurface faces the object side, a second lens of a convex lens, a thirdlens of a concave meniscus lens whose convex surface faces the objectside, a fourth lens L4 of a convex lens, a triple-cemented lens made ofa fifth lens of a concave meniscus lens whose convex surface faces theobject side, a sixth lens of a convex lens and a seventh lens of aconcave meniscus lens whose concave surface faces the object side, andan eighth lens of a convex lens, which lenses are arrayed in order fromthe object side.
 16. The zoom lens as described in claim 12,characterized in that: said first lens group comprises a first lens of aconcave meniscus lens whose convex surface faces the object side, asecond lens of a convex lens, a third lens of a concave meniscus lenswhose convex surface faces the object side, a fourth lens L4 of a convexlens, a triple-cemented lens made of a fifth lens of a concave meniscuslens whose convex surface faces the object side, a sixth lens of aconvex lens and a seventh lens of a concave meniscus lens whose concavesurface faces the object side, and an eighth lens of a convex lens,which lenses are arrayed in order from the object side.
 17. The zoomlens as described in claim 9, characterized in that: said first lensgroup comprises a first lens of a concave meniscus lens whose convexsurface faces the object side, a second lens of a convex lens, acemented lens made of a third lens L3 of a concave meniscus lens whoseconvex surface faces the object side and a fourth lens of a convex lens,a triple-cemented lens made of a fifth lens of a concave meniscus lenswhose convex surface faces the object side, a sixth lens of a convexlens and a seventh lens of a concave meniscus lens whose concave surfacefaces the object side, and an eighth lens of a convex lens, which lensesare arrayed in order from the object side.
 18. The zoom lens asdescribed in claim 10, characterized in that: said first lens groupcomprises a first lens of a concave meniscus lens whose convex surfacefaces the object side, a second lens of a convex lens, a cemented lensmade of a third lens L3 of a concave meniscus lens whose convex surfacefaces the object side and a fourth lens of a convex lens, atriple-cemented lens made of a fifth lens of a concave meniscus lenswhose convex surface faces the object side, a sixth lens of a convexlens and a seventh lens of a concave meniscus lens whose concave surfacefaces the object side, and an eighth lens of a convex lens, which lensesare arrayed in order from the object side.
 19. The zoom lens asdescribed in claim 11, characterized in that: said first lens groupcomprises a first lens of a concave meniscus lens whose convex surfacefaces the object side, a second lens of a convex lens, a cemented lensmade of a third lens L3 of a concave meniscus lens whose convex surfacefaces the object side and a fourth lens of a convex lens, atriple-cemented lens made of a fifth lens of a concave meniscus lenswhose convex surface faces the object side, a sixth lens of a convexlens and a seventh lens of a concave meniscus lens whose concave surfacefaces the object side, and an eighth lens of a convex lens, which lensesare arrayed in order from the object side.
 20. The zoom lens asdescribed in claim 12, characterized in that: said first lens groupcomprises a first lens of a concave meniscus lens whose convex surfacefaces the object side, a second lens of a convex lens, a cemented lensmade of a third lens L3 of a concave meniscus lens whose convex surfacefaces the object side and a fourth lens of a convex lens, atriple-cemented lens made of a fifth lens of a concave meniscus lenswhose convex surface faces the object side, a sixth lens of a convexlens and a seventh lens of a concave meniscus lens whose concave surfacefaces the object side, and an eighth lens of a convex lens, which lensesare arrayed in order from the object side.
 21. An imaging apparatushaving a zoom lens, imaging means for transforming an image taken in bysaid zoom lens to an electrical image signal, and image control means,characterized in that: said image control means, referring to atransformation coordinate coefficient provided in advance according to avariable power rate by said zoom lens, moves points on the image whichare defined by the image signal formed by said imaging means to form anew image signal subjected to coordinate transformation and to outputsaid new image signal, said zoom lens of an inner focus type having fouror five lens groups, comprises at least a first lens group havingpositive refractive power, a second lens group having negativerefractive power, which is movable in an optical axis direction mainlyfor zooming (varying power), a third lens group having positiverefractive power, and a fourth lens group having positive or negativerefractive power, which is movable in the optical axis direction forcorrecting fluctuations in focal position during zooming and forfocusing, which lens groups are arrayed in order from an object side,and said first lens group comprises at least a concave lens, a convexlens, and a triple-cemented lens in which a lens made of speciallow-dispersion glass is sandwiched in the middle, which lenses arearrayed in order from the object side.
 22. The imaging apparatus asdescribed in claim 21, characterized in that: said triple-cemented lensin said first lens group includes a first concave lens A1, a convex lensA2 formed of special low-dispersion glass and a second concave lens A3,which lenses are arrayed in order from the object side, and said firstconcave lens A1 and said convex lens A2 are formed of materialssatisfying the following two conditional formulae (1) and (2):n1−n2>0.3  (1)|v1−v2|>40  (2) wherein refractive indexes at a line C, a line d, a lineF and a line g are nC, nd, nF and ng, respectively, and nx is arefractive index nd at the line d of a lens Ax (an xth lens from theobject side among the triple-cemented lens, hereinafter, this is thesame), and vx is an Abbe number vd=(nd−1)/(nF−nC) at the line d of thelens Ax.
 23. The imaging apparatus as described in claim 21,characterized in that: said triple-cemented lens in said first lensgroup includes a first concave lens A1, a convex lens A2 formed ofspecial low-dispersion glass and a second concave lens A3, which lensesare arrayed in order from the object side, and said convex lens A2 andsaid second concave lens A3 are formed of materials satisfying thefollowing three conditional formulae (3), (4), and (5):|n2−n3|<0.1  (3)v23>80  (4)ΔP23>0.03  (5) wherein refractive indexes at a line C, a line d, a lineF and a line g are nC, nd, nF and ng, respectively, and nx is arefractive index nd at the line d of a lens Ax (an xth lens from theobject side among the triple-cemented lens, hereinafter, this is thesame), vx is an Abbe number vd=(nd−1)/(nF−nC) at the line d of the lensAx, and Px is a partial dispersion ratio P=(ng−nF)/(nF−nC) of the lensAx.
 24. The imaging apparatus as described in claim 22, characterized inthat: said triple-cemented lens in said first lens group includes afirst concave lens A1, a convex lens A2 formed of special low-dispersionglass and a second concave lens A3, which lenses are arrayed in orderfrom the object side, and said convex lens A2 and said second concavelens A3 are formed of materials satisfying the following threeconditional formulae (3), (4), and (5):|n2−n3|<0.1  (3)v23>80  (4)ΔP23>0.03  (5) wherein refractive indexes at a line C, a line d, a lineF and a line g are nC, nd, nF and ng, respectively, and nx is arefractive index nd at the line d of a lens Ax (an xth lens from theobject side among the triple-cemented lens, hereinafter, this is thesame), vx is an Abbe number vd=(nd−1)/(nF−nC) at the line d of the lensAx, and Px is a partial dispersion ratio P=(ng−nF)/(nF−nC) of the lensAx.
 25. The imaging apparatus as described in claim 21, characterized inthat: said first lens group comprises a first lens of a concave meniscuslens whose convex surface faces the object side, a second lens of aconvex lens, a triple-cemented lens made of a third lens of a concavemeniscus lens whose convex surface faces the object side, a fourth lensof a convex lens and a fifth lens of a concave meniscus lens whoseconcave surface faces the object side, and a sixth lens of a convexlens, which lenses are arrayed in order from the object side.
 26. Theimaging apparatus as described in claim 22, characterized in that: saidfirst lens group comprises a first lens of a concave meniscus lens whoseconvex surface faces the object side, a second lens of a convex lens, atriple-cemented lens made of a third lens of a concave meniscus lenswhose convex surface faces the object side, a fourth lens of a convexlens and a fifth lens of a concave meniscus lens whose concave surfacefaces the object side, and a sixth lens of a convex lens, which lensesare arrayed in order from the object side.
 27. The imaging apparatus asdescribed in claim 23, characterized in that: said first lens groupcomprises a first lens of a concave meniscus lens whose convex surfacefaces the object side, a second lens of a convex lens, a triple-cementedlens made of a third lens of a concave meniscus lens whose convexsurface faces the object side, a fourth lens of a convex lens and afifth lens of a concave meniscus lens whose concave surface faces theobject side, and a sixth lens of a convex lens, which lenses are arrayedin order from the object side.
 28. The imaging apparatus as described inclaim 24, characterized in that: said first lens group comprises a firstlens of a concave meniscus lens whose convex surface faces the objectside, a second lens of a convex lens, a triple-cemented lens made of athird lens of a concave meniscus lens whose convex surface faces theobject side, a fourth lens of a convex lens and a fifth lens of aconcave meniscus lens whose concave surface faces the object side, and asixth lens of a convex lens, which lenses are arrayed in order from theobject side.